American super lightweight boxer Ryan Garcia has denied taking a banned performance-enhancing substance before his victory over WBC world champion Devin Haney in New York last month.

ESPN, citing a leaked letter from the Voluntary Anti-Doping Association (VADA), reported on Wednesday that Garcia had tested positive for ostarine on the day before and day of the fight.

Garcia addressed the report in a video posted on X.

"Everybody knows that I don't cheat," the 25-year-old said.

"Never taken a steroid. ... I don't even know where to get steroids at the end of the day, I barely take supplements. Big lies ..."

Garcia floored Haney three times on the way to a majority decision at Brooklyn's Barclays Center to hand his rival the first defeat of his professional career. He missed weight so was unable to claim the title.

Ostarine is a selective androgen receptor modulator which produces similar results to anabolic steroids, allowing athletes to increase muscle mass, stamina and fitness. It is banned by the World Anti-Doping Agency (WADA).

VADA, an independent agency based in Las Vegas that runs testing mostly for boxing and mixed martial arts, did not immediately respond to a request for comment.